As shown in FIG. 1, this kind of optical switch includes at least one input port 11 to which a light beam generated outside is inputted through, for example, an optical fiber and the like and from which the light beam is emitted, a mirror 30 driven while being inserted and removed in and from the optical path of a light beam 40 emitted from the input port 11, first and second output ports 21 and 22 for receiving the light beam from the input port and outputting the light beam to the outside, and a drive 35 for driving the mirror. In the present invention, since a light beam is supplied to the input port 11 from the outside, the input port 11 is referred to as an input port. However, in reality, the input port 11 emits the supplied light beam. Although the light beam is incident on the output ports 21 and 22, the output ports 21 and 22 are referred to as output ports because the output ports 21 and 22 output the supplied light beam to the outside. The following is an example where a mirror is used as a reflector.
When the mirror 30 is inserted in an optical path, the light beam 40 emitted from the input port 11 is reflected by the mirror 30 and is coupled to the first output port 21. Further, when the mirror 30 is removed from the optical path, the light beam from the input port 11 travels straight as it is and is coupled to the second output port 22. In this way, in this kind of optical switch, the mirror 30 is inserted and removed to switch outputs to the first output port 21 and the second output port 22. A solid line arrow in FIG. 1 indicates the optical axis of the light beam 40 emitted from the input port and dotted lines extending in parallel with respect to the solid line arrow indicate the beam diameter of the light beam.
In this optical switch, when inserted, the mirror 30 has to sufficiently reflect the light beam and couple the light beam to the first output port 21 to reduce an insertion loss. Further, for the second output port 22, the mirror 30 has to sufficiently block the light beam to prevent crosstalk to the second output port. However, it is not possible to perfectly prevent crosstalk and thus a reduction in crosstalk will be described in the following explanation. When removed, the mirror 30 has to sufficiently allow coupling of the light beam to the second output port 22 to reduce an insertion loss and has to prevent reflection toward the first output port 21 to reduce crosstalk to the first output port.
Conventionally, in order to reduce an insertion loss on one of the output ports and reduce crosstalk on the other output port when a mirror is inserted and removed, the mirror is made, for example, sufficiently larger than the beam diameter of the light beam 40. Generally as shown in FIG. 1A, the mirror 30 is inserted to sufficiently intersect the light beam when inserted. Further, generally as shown in FIG. 1C, the mirror 30 is sufficiently moved away from the light beam when removed (for example, reference 1: Japanese Patent Application Laid-Open No. 2004-354458).
As described above, conventionally in order to reduce an insertion loss and crosstalk, it is recognized that the driving stroke of the mirror 30 has to have a length ST1 as shown in FIG. 1C. For this reason, the load of a mirror driving mechanism is increased.